A conventional form of brushroll comprises a wood spindle which carries a plurality of tufts of bristles or beater bar elements. The brushroll is rotatably supported at both ends by end assemblies mounted in the vacuum cleaner nozzle. Each end assembly includes a disk carried on the end of the spindle, a pin fixed to the spindle and projecting from its end through the disk, a bearing having its inner race fixed on the projecting end of the pin, and an end cap having a pocket that receives the outer race of the bearing. The end caps mount the spindle for rotation in the nozzle of the vacuum cleaner. In a belt driven spindle arrangement, one of the pins extends through an end cap and a pulley is threaded onto the pin so that the spindle can be rotated by a belt connected to the vacuum cleaner motor.
In a known construction over which the present invention is an improvement, one end of the pin that carries the pulley is knurled and is frictionally engaged in a hole in the spindle. The knurling on the pin stops short of the outer face of the end cap. During assembly, the pulley would be threaded onto the end of the pin until the bearing was captured between the pulley and the disk at the end of the spindle. With the prior art design, it was possible to continue to thread the pulley on the pin. Since the bearing was already engaged with the plastic disk, this continued threading of the pulley would withdraw the pin endwise from the hole in the spindle.
The movement of the pin caused by overthreading the pulley onto the pin would unbalance the brushroll which typically rotates at speeds of 5500-6000 rpm. The unbalanced condition results in eccentric rotation. The pin would wobble in the hole of the spindle and enlarge it, which results in brushroll rattle and general unsatisfactory operation.
The problem is accentuated when large die cast pulleys are used. The larger die cast pulleys are themselves unbalanced. As the pin supporting the pulley is withdrawn from the hole, the unbalanced large pulleys accentuate wobbling of the pin.